2.3.1. Good Practices¶
2.3.1.1. Stop using = operator to create a copy of a Python list. Use copy method instead¶
When you create a copy of a Python list using the = operator, a change in the new list will lead to the change in the old list. It is because both lists point to the same object.
l1 = [1, 2, 3]
l2 = l1
l2.append(4)
l2
[1, 2, 3, 4]
l1
[1, 2, 3, 4]
Instead of using = operator, use copy() method. Now your old list will not change when you change your new list.
l1 = [1, 2, 3]
l2 = l1.copy()
l2.append(4)
l2
[1, 2, 3, 4]
l1
[1, 2, 3]
2.3.1.2. Enumerate: Get Counter and Value While Looping¶
Are you using for i in range(len(array)) to access both the index and the value of the array? If so, use enumerate instead. It produces the same result but it is much cleaner.
arr = ['a', 'b', 'c', 'd', 'e']
# Instead of this
for i in range(len(arr)):
print(i, arr[i])
0 a
1 b
2 c
3 d
4 e
# Use this
for i, val in enumerate(arr):
print(i, val)
0 a
1 b
2 c
3 d
4 e
2.3.1.3. Difference between list append and list extend¶
If you want to add a list to another list, use the append method. To add elements of a list to another list, use the extend method.
# Add a list to a list
a = [1, 2, 3, 4]
a.append([5, 6])
a
[1, 2, 3, 4, [5, 6]]
a = [1, 2, 3, 4]
a.extend([5, 6])
a
[1, 2, 3, 4, 5, 6]